PHP生成条形图的方法

<?php
? // create an array of values for the chart. These values?
? // could come from anywhere,POST,GET,database etc.?
? $values = array(23,32,35,57,12,3,36,54,15,43,24,30);
?
? // now we get the number of values in the array. this will?
? // tell us how many columns to plot?
??? $columns? = count($values);
?
? // set the height and width of the graph image
?
??? $width = 300;?
??? $height = 200;
?
? // Set the amount of space between each column?
??? $padding = 5;
?
? // Get the width of 1 column?
??? $column_width = $width / $columns ;
?
? // set the graph color variables?
??? $im??????? = imagecreate($width,$height);?
??? $gray????? = imagecolorallocate ($im,0xcc,0xcc);?
??? $gray_lite = imagecolorallocate ($im,0xee,0xee);?
??? $gray_dark = imagecolorallocate ($im,0x7f,0x7f);?
??? $white???? = imagecolorallocate ($im,0xff,0xff);
?
? // set the background color of the graph?
??? imagefilledrectangle($im,$width,$height,$white);
?
?
? // Calculate the maximum value we are going to plot?
? $max_value = max($values);
?
? // loop over the array of columns?
??? for($i=0;$i<$columns;$i++)?
??????? {
??? // set the column hieght for each value?
??????? $column_height = ($height / 100) * (( $values[$i] / $max_value)
?
*100);?
??? // now the coords
??????? $x1 = $i*$column_width;?
??????? $y1 = $height-$column_height;?
??????? $x2 = (($i+1)*$column_width)-$padding;?
??????? $y2 = $height;
?
??????? // write the columns over the background?
??????? imagefilledrectangle($im,$x1,$y1,$x2,$y2,$gray);
?
??????? // This gives the columns a little 3d effect?
??????? imageline($im,$gray_lite);?
??????? imageline($im,$gray_dark);?
??????? }
?
?? // set the correct png headers?
?? header ("Content-type: image/png");?
? // spit the image out the other end?
? imagepng($im);?
?>